Tuning the Threshold Voltage of an Oxide Thin-Film Transistor by Electron Injection Control Using a p−n Semiconductor Heterojunction Structure

Herein, a heterojunction structure integrating p-type tellurium (Te) and n-type aluminum-doped indium−zinc-tin oxide (Al:IZTO) is shown to precisely modulate the threshold voltage (V_T) of the oxide thin-film transistor (TFT). The proposed architecture integrates Te as an electron-blocking layer and Al:IZTO as a charge-carrier transporting layer, thereby enabling controlled electron injection. The effects of incorporating the Te layer onto Al:IZTO are investigated, with a focus on X-ray photoelectron spectroscopy (XPS) analysis, in order to explain the behavior of oxygen vacancies and to depict the energy band structure configurations. By modulating the thickness and employing both single and double deposition methods for the heterojunction Te layer, a remarkable V_T shift of up to +20 V is achieved. Furthermore, this study also shows excellent stability to a positive bias stress of +2 MV/cm for 10,000 s without additional passivation layers, demonstrating the robustness of the designed TFT. By a thorough optimization of the Al:IZTO/Te interface, the results demonstrate not only the substantial impact of the introduced heterojunction structure on V_T control but also the endurance, durability, and stability of the optimized TFTs under prolonged long-term operating stress, thus offering promising prospects for tailored semiconductor device applications.